In vehicles having hybrid drive, the internal combustion engine is shut down, as a rule, during standstill phases via an appropriate start-stop function for a broadened savings in fuel consumption. Since hybrid vehicles have electric motors of clearly greater performance power instead of conventional starters, it is possible to have great comfort during an automatic engine start after a start-stop phase.
The automatic stop operation in hybrid vehicles is generally initiated only when the engine is within the range of idling speed or has reached it. However, because of this, the internal combustion engine is intercepted from a deceleration fuel cutoff, that was possibly initiated previously, by the idle-speed controller above the idling speed (restart speed), and is brought down to the required idling speed. This is required, since after falling below the restart speed, the engine speed would drop off in an uncontrolled manner, and stalling would occur in the worst case. Besides stressing the bearings, such a jolting shutdown is not desirable from a comfort point of view. this procedure reduces the maximum consumption advantage that can be achieved by the stop operation of the internal combustion engine by the duration of the active idle-speed controller.